The project — replacing nearly 80 miles of pipeline in the most populated region of Colorado — included a lot of public outreach and education by owner Xcel Energy. And construction work made the news, particularly when it affected traffic.
Global Underground took steps to keep its jobsites as clean as possible, especially when it came to drilling fluids. It also kept its footprint small because several of the bores were in constricted areas, with some in urban settings along high-traffic roads. So company president and CEO Robert Meadows turned to a new machine, a Vermeer D220x300 Navigator horizontal directional drill, which he felt had the power to install the 16-in. steel pipeline and the compact size he needed.
“Some of the setups required us to fit our equipment off the road in tight right of ways where any other rig with 30,200 ft-lbs of rotary torque would not fit,” Meadows said. “The onboard pump, cab and rod loader helped us fit into less space and still have the power to get out over 2,000-ft bores.”
Global Underground’s work is part of a multi-year natural gas pipeline project by Xcel Energy. Plans call for the replacement of 77 miles of high-pressure transmission pipeline from north of Fort Collins near the border with Wyoming to just outside the northwestern suburbs of Denver.
The project is part of Xcel Energy’s pipeline integrity management program and is intended to continue to provide reliable and safe natural gas service to current and new customers along the Front Range, which is the heavily populated region just east of the Rocky Mountains.
This has been a prominent project from the beginning. Xcel held open houses before construction started in 2012, has released materials to educate the public and created a website dedicated to the project.
Global Underground was hired by the general contractor Blackeagle Energy Services. It is not the only company doing HDD work, but it has completed two segments of the project and started a third earlier this year.
Meadows founded Global Underground in Colorado Springs in 1999 with just one directional drill, and the company grew along with the then-booming telecommunications industry. As telecommunication infrastructure needs waned, Global Underground expanded into the municipal market and used trenchless technologies for work that cities had traditionally handled with open-cut methods, such as on-grade sewers.
The company does wet and dry utilities, including water, sewer, electric, telecommunications, natural gas and petroleum using a variety of trenchless methods. It now has 11 drills and also does open-cut work.
“We do pretty much everything,” Meadows says. “In this market, you have to be diverse. You’ve got to have crews doing an on-grade sewer one day and an electric bore the next.”
Six Bores, Tight Space
For the Xcel Energy Colorado pipeline project, Global Underground completed six bores over two different segments last year and is again working on the project. The common theme throughout was a confined work space and the notoriously diverse Colorado ground conditions.
What was Global Underground’s first phase included two bores, one about 1,900 ft and the other 1,100 ft on the north side of Fort Collins. This occurred on a major street with very heavy traffic. Ground conditions included sand, gravel, cobble, sandstone and shale.
The second phase had four bores: two at 2,200 ft each, 1,700 ft and 1,600 ft. The work was in rural areas farther south down the pipeline route, but setup space was a major issue with the drilling being done on a tight right of way on the side of a two-lane road. Ground conditions included shale, clay and a sandstone material with a lot of groundwater.
Those varying ground conditions are a fact of life in Colorado. “We have every kind of material, from 40,000 psi granite to sandstone to shale to cobble,” Meadows says. “We’re used to the conditions. It’s just every bore is different.”
Global Underground needed to be able to work in confined areas but have the power to install a 16-in. steel pipeline in a variety of ground conditions and anywhere from 5 to 50 ft below surface. The company used a Vermeer D220x300 HDD on both phases, plus a Vermeer D330x500 Navigator drill on the second job.
The D220x300 has a compact footprint with a maximum thrust/pullback rating of 242,100 lbs.
“It has quite a bit of power in a small package, and it’s been really needed in this market,” Meadows says. “As rights of way get tighter and more congested, you need to be able to get machines with more power with a smaller setup into tight locations.”
On the pilot bores done by the D220x300, Global Underground used a 2-degree bent sub with a mud motor or a jetting assembly and an 8.75-in. mill tooth bit.
On all of the bores, it push reamed with a 16-in. reamer and then back reamed with a 24-in. reamer.
Global Underground took other measures to alleviate any concerns with drilling in compact, populated areas. To keep the worksites cleaner and less congested, it used a mud line and pumped the drilling fluids from the exit pit back to the entrance pit using 4-in. polyethylene pipe.
The fluids were then pumped out of the entrance pit and into a reclaimer. This meant the drilling fluids did not need to be hauled back to the reclaimer in large 80-barrel vacuum trucks. “It was cleaner, less noisy and not as congested with those trucks off the road,” Meadows says.
The mud line is common practice for Global Underground, but Xcel Energy and Blackeagle Energy Services had never had a contractor do that on their projects and were impressed. “When we are out on a project we realize that we represent not only the general contractor that we’re working for, but also the facility owner,” Meadows says. “The general public, when they look at your jobsite and it’s clean and you don’t have mud running up underneath your equipment out in the street, all of your containment is in place, constantly maintained, your equipment is kept clean — that makes an impression.”
Lots of Water
Global Underground ran into another issue that required ingenuity. Once the pilot hole was completed on the first bore of the second segment, it encountered what was basically an underground stream, and the water volume entering the exit pit was at a higher level than what was being pumped downhole. The problem was made more complicated by the exit pit being 45 ft lower than the entrance pit.
The water drastically altered the viscosity of the drilling fluids. The crew added soda ash to counteract the pH levels that were changed by the water and to build the viscosity to the required level. Crew members also had to dewater the exit pit 24 hours a day for the one-month duration of that bore.
Even after the pipe was installed, the water kept running. So rock was laid down to act as a filter and, after the water was tested to ensure there were no contaminants, it was redirected to a nearby irrigation ditch, which pleased the local farmers.
Groundwater was shown on the geotechnical reports, but Meadows says contractors don’t always know the actual volume of the water. Water volume can be hard to predict because it could depend on the time of year the test was conducted and whether the volume changed when construction began.
“You have to take soil investigations with a grain of salt and use that information the best you can,” he says. “Plan for the project but know that it’s not an absolute of what you’re going to run into.”
Meadows believes his crew’s ability to problem-solve, its use of the mud line and its proficiency in the confined jobsites helped it land additional phases of the project. It started its third job for Xcel Energy and Blackeagle Energy Services in March. It is using its D220x300 HDD on bores of 3,500 ft and 1,500 ft to install 12-in. natural gas pipeline up to 45 ft deep.
“Once we started working for them, they wanted us there with them as part of their team,” he says. “They enjoy our processes. They enjoy our equipment.”
Gregg Hennigan is a features writer for Two Rivers Marketing, Des Moines, Iowa.